The Pospiviroidae[1] are a incertae sedis family of ssRNA viroids with 5 genera and 39 species, including the first viroid to be discovered, PSTVd, which is part of genus Pospiviroid.[2] Their secondary structure is key to their biological activity. The classification of this family is based on differences in the conserved central region sequence.[3] Pospiviroidae replication occurs in an asymmetric fashion via host cell RNA polymerase, RNase, and RNA ligase. Its hosts are plants, specifically dicotyledons and some monocotyledons.
| Pospiviroidae | |
|---|---|
Virus classification  | |
| (unranked): | Viroid |
| Family: | Pospiviroidae |
| Genera | |
Genome
Members of the family Pospiviroidae have circular ssRNA of 246–375 nt. They assume rod-like or quasi-rod-like conformations containing a central conserved region (CCR) and a terminal conserved hairpin (TCH) or a terminal conserved region (TCR). The genome of viroids does not encode any proteins.[4]
Replication
 | This section may be too technical for most readers to understand. (August 2023) |
Its replication is nuclear and mediated by DNA-dependent RNA polymerase II, which is redirected to use RNA templates through an asymmetric RNA–RNA rolling-circle mechanism. (+) polarity circRNA molecules (by convention the most abundant strand in vivo) are repeatedly transcribed into oligomeric complementary (−) RNAs. Such intermediates serve as templates for generating oligomeric (+) RNAs that are cleaved by a host enzyme of the RNase III class. The termini of the resulting linear monomers are ligated by the host DNA ligase 1 to generate the mature circular viroid RNA.[4]
Taxonomy
- Apple dimple fruit viroid
- Apple scar skin viroid
- Apscaviroid aclsvd
- Apscaviroid cvd-VII
- Apscaviroid dvd
- Apscaviroid glvd
- Apscaviroid lvd
- Apscaviroid plvd-I
- Apscaviroid pvd
- Apscaviroid pvd-2
- Australian grapevine viroid
- Citrus bent leaf viroid
- Citrus dwarfing viroid
- Citrus viroid V
- Citrus viroid VI
- Grapevine yellow speckle viroid 1
- Grapevine yellow speckle viroid 2
- Pear blister canker viroid
- Citrus bark cracking viroid
- Coconut cadang-cadang viroid
- Coconut tinangaja viroid
- Hop latent viroid
- Coleus blumei viroid 1
- Coleus blumei viroid 2
- Coleus blumei viroid 3
- Coleviroid cbvd-5
- Coleviroid cbvd-6
- Dahlia latent viroid
- Hop stunt viroid
- Chrysanthemum stunt viroid
- Citrus exocortis viroid
- Columnea latent viroid
- Iresine viroid 1
- Pepper chat fruit viroid
- Pospiviroid plvd
- Potato spindle tuber viroid
- Tomato apical stunt viroid
- Tomato chlorotic dwarf viroid
- Tomato planta macho viroid
References
External links
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